1. Field of the Invention
The present invention is directed to an electrode system intended for proximal connection to a cardioverter/defibrillator, and for distal placement in the region of the heart in order to deliver electrical energy to the heart from the cardioverter/defibrillator to terminate an arrhythmia in the heart, and in particular to such an electrode system having at least two electrodes.
2. Description of the Prior Art
In defibrillation/cardioversion (cardioversion in this context meaning a lower energy defibrillation; the generic designation ("defibrillation" will be used hereinafter) using, for example, a three-electrode system with two intravascular electrodes, one of these intravascular electrodes is normally placed in the right ventricle, and another either in the superior vena cava or, less commonly, in the inferior vena cava. It is also known to place one of the electrodes in the coronary sinus and its tributary along the base of the heart (i.e., the portion of the great cardiac vein which runs along the base of the heart). In order to achieve a highly efficient utilization of the energy stored in the defibrillator, as well as to achieve good distribution of current in the heart while simultaneously avoiding the need for major surgery (thoracostomy), the third electrode is devised as a subcutaneous, large-area electrode, i.e., a patch electrode. The patch electrode is usually placed in the vicinity of the left ventricle, between the patient's ribs and skin.
An electrode systems with the above-described vascular placement is disclosed in U.S. Pat. No. 4,708,145. This patent discloses intravascular electrodes carried on a common electrode cable for a plurality of electrodes in the right ventricle and the superior vena cava. It is also known to provide separate electrode cables for different electrodes, and a separate sensor electrode for a sensor for detecting cardiac events. Such versions of electrode systems are disclosed in U.S. Pat. No. 4,727,877, European Application 0 373 953 and U.S. Pat. No. 5,044,375.
The use of systems with only two (non-epicardiac) electrodes is also known. An example of such a system is disclosed in U.S. Pat. No. 3,942,536, in which the electrodes, carried on a common electrode cable, are placed in the superior vena cava and the right ventricle, respectively.
In those systems which make use of the coronary vessels on the venous side of the heart as a site for at least one of the defibrillation electrodes, the coronary vessels which have been employed for this purpose are the coronary sinus and its tributary (a portion of great cardiac vein) running along the base of the heart, i.e, along the valve plane of the heart.